Crystal and molecular structures of 6β-bromoacetyl- and 6β-chloroacetyl-3,5α-cyclo-5α-cholestane (i-cholesteryl bromoacetate and chloroacetate)

Abstract

The crystal structures of i-cholesteryl bromoacetate and chloroacetate have been elucidated by X-ray crystallo-graphic analysis. The bromoacetate was solved by heavy atom methods, and the chloroacetate by non-centrosymmetric direct methods. The two structures are not isomorphous: the bromoacetate is orthorhombic, while the chloroacetate is monoclinic and has given the more accurate molecular parameters. In both molecules, as expected from chemical and spectral evidence, positions 3 and 5 have linked to form a cyclopropane ring, the plane of which is nearly normal to that of the rest of the sterol skeleton. Conformational differences are observed in the side chains.